Process of manufacturing porous bodies.



STATES PATENT OFFICE.

-lBOTHO SCH'WEliIN, 0F FRANKFORT-ON-THE-MAIN, GERMANY.

PROCESS OF MANUFACTURTNG POROUS BODIES.

No Drawing.

' but still hig y To all whom it may concern:

Be it knownthat I, Bo'rno SCHWERIN, a subject of the German Em eror, and a resident of Frankfort-on-the d'ain, Germany, have invented certain new and useful Improvements in Processes of Manufacturing Porous Bodies, of which the following is aspecification.

My invention relates toimprovements in a process of manufacturing porous bodies from carborundum, corundum, and the like.

The object'of the improvements is to provide a product which by reason of its purity is partlcularly suitable for chemical, electrochemical and other purposes, which can be used in the manufacture of dia hragms, and which is very porous and a apted to absorb large quantitles of water. a

If the roduct is 'to be made for example from. car orundum or corundum, the process is carried out as follows: The raw material is finely ground and elutriated.v The elut'riation is advanta eously carried out by, suspending the finely round material in water to which is a ded a basic substance such as ammonia the material treated is of an electro-negative such as carborundum for exampositive character, as corundum, an acid such as acetic acid is added. To the finest partlcles thus obtained which have been separated from the coarser particles by the elutriation and suspension inthe water used for the elutriation, and hence-obtained in an exceedingly finely dividedcondition, and in a condition comparable with that of particles of a colloidal nature, enough water is added to. produce a paste which can be formed or molded into the desired shape.

'The articles thus formed or molded are dried and burned to form the desired roduct. Owing to the finely divided con ition of the particles used and their properties which partake of a colloidal nature, the refractory materials used, such as carborun dum or corundum, which in theirnatural state arenot plastic and are inca able of being molded and burned, are rend pableof being somolded and burned, without the addition of'any foreign binding medium. They are thus converted from materials naturally non-plastic into a condition comparable with that of the natural plastics such as clay, and can be molded and burned to form porous and coherent,

Specification 01 Letters Patent. Application filed February 17, 1911.

ered ca-.

PatentedMay 21, 1912. Serial No. 608,148.

sistive, products.

burning is advantageously carried out in a non-oxidizing or reducing atmosphere since an oxidizing fire or an oxidizin current of air would convert a portion 0 divided carborundum into silicic acid the presence of which in the final product would render the latter liable to crack or expand.

The present process differs from processes heretofore 1n use in that the particles of the resulting products are not bound to gether by meltmg or fusion, nor by means of a molten bindingmedium, but are formed into a coherent porous mass by being brought into direct contact with one another and b burning. No fusible flux or binding me ium is therefore present in the resulting product;

It is sometimes advantageous to carry out the process by ,addin ,to the material an unstable or removab e bindin medium such, for example, as starch, w ich either disappears in the course of the further treatment of the material, or is afterward removed. As carborundum does not melt at all, and corundum only at the highest temperatures, the burning temperature may be varied within-large limits.

The process may be further improved by. t e material treated (carremovmg from borundum, corundum, etc.) any natural impurities such as iron compounds, or any foreign substances such as particles that may have been ing the material, by successively boiling the same with concentrated hydrochloric acid, nitrohydrochloric acid, hydrofluoric *acid, and concentrated soda lye. Between each "boiling operation the material is filtered and thoroughly washed: After being. thus thoroughly cleaned the substances have properties which they do not possess in an uncleaned state. For example the conductivity which before was big is reduced almost to zero, and the stability under chemical influences is increased.

Thev articles made from the material are hard and have a metallic sound. Theydo not chan e their form when burning 'the same, an their surfaces are not changed. The articles may be made either with a rough or smooth surface or a reflecting surface may even be imparted thereto, for which purposes they are molded or formed either on refractory and strongl re- In the case of suc an oxidizable material as carborundum the.

of iron introduced when grindthe finely a rough, smooth or reflecting surface. Pat terns or sketches which are applied thereto before drying and burning are not changed by the burningprocess. As the articles do not contain any foreign matter, they have the stability of the carborundum or corundum, and they may be used for various purposes, for example in the manufacture of diaphragms. Diaphragms made from my improved material are suitable for example for electrolytic purposes, in which case at one side of the diaphragm there may be an acid and at the opposite side an alkaline electrolyte. The porosity of the material is large and it depends exclusively on the size of the parts, the porosity being larger if the material is made of smaller particles.

The articles made by my process can be used wherever a material is required, which has a high de cc of porosity, which is refractory, una ected by chemical influences and hard, and which does not change its form.

In burning porcelain a reducing atmosphere has been used. However, in this case the use of a reducing atmosphere has no infiuence on theburning process as such. The hardening of the porcelain and the change 7 of the structure and shape caused by the hardening are exactly the same, whether burning be efiected in a reducing or in an oxidizing atmosphere, because the material subjected to the burning process is not itself subjected to. oxidation. In this case the reducing atmosphere has exclusively the function to reduce the impurities of the material which consist of the coloring iron oxid into the colorless protoxid. In my improved process, however, materials are treated which, at the necessary temperature, are themselves subjected to oxidation by the oxid of the air.

I claim herein as my invention:

1. The herein described process of producing articles of carborundum, corundum, and similar refractory materials which comprises grinding the raw material, separating from the finely ground material the finest particles by elutriation, molding the same, and burning the molded article.

2. The hereinv described process of producing articles of carborundum, corundum,

and similar refractory material, which comraw material, cleaning the same, separating from the finely ground and cleaned material the finest particles by elutri'ation molding'the same, and burning the molde article.

prises grinding the 3. The herein described process of pro- 1 ducing articles of carborundum, which comprises grinding'the crude material, separatin from the finely ground material the finest particles by elntriation, molding the same, and burning the molded article in a non-oxidizing atmosphere.

In testimony whereofl have signed my name to this specification in the presence of two subscribing witnesses.

BOTHQ SCHWERIN.

Witnesses:

JEAN Gmmn v FRIEDEL COLLISCHANN. 

